Could not start process "mingw32-make.exe" qmake_all

Hi guys,
I am new to Qt. I got this source code which was written using Qt as the project has .pro extension. I thought that easy, I can open it with Qt or Qt creator ( what is the difference between this 2 guys?). I spent the last week trying to install Qt creator but no luck and I was going round in circle trying different things and now I gave up and I am asking help.
I used the installation file "qt-unified-windows-x86-3.0.2-online" from Qt website and I installed Qt creator 4.6.0 and the installation was ok. I created a Hello Word project just to see if it works but it didn't . I got this error message :( Compiler output)
09:12:11: Running steps for project rob5...
09:12:11: Starting: "C:\Qt\5.9.3\mingw53_32\bin\qmake.exe" "C:\Users\rabmerab\Documents\Qt projects\rab5\rab5.pro" -spec win32-g++ "CONFIG+=debug" "CONFIG+=qml_debug"
09:12:13: The process "C:\Qt\5.9.3\mingw53_32\bin\qmake.exe" exited normally.
09:12:13: Could not start process "mingw32-make.exe" qmake_all
Error while building/deploying project rab5 (kit: Desktop Qt 5.9.3 MinGW 32bit)
The kit Desktop Qt 5.9.3 MinGW 32bit has configuration issues which might be the root cause for this problem.
When executing step "qmake"
09:12:13: Elapsed time: 00:02.

I searched manually for the file mingw32-make.exe in Q folder and program folder but nowhere to be seen.
Can someone put some light on this issue?
Many thanks in advance

My first installation issue is resolved. After 03 or 04 clean installation, now I can compile and run Hello Word project in the Qt Creator 4.5.1 which is good. But the headache start again with the second part of the exercise.
Now the more important part is to open the project and add more functionalities. It has a graphical Interface and I wanted to add one button. I manage to open the project but when I build the project, I had this error.
Does anyone have the slight idea how to resolve this issue?
Your help would be very appreciated !

My first installation issue is resolved. After 03 or 04 clean installation, now I can compile and run Hello Word project in the Qt Creator 4.5.1 which is good. But the headache start again with the second part of the exercise.
Now the more important part is to open the project and add more functionalities. It has a graphical Interface and I wanted to add one button. I manage to open the project but when I build the project, I had this error.
Does anyone have the slight idea how to resolve this issue?
Your help would be very appreciated !